Method of cracking hydrocarbon oils



Aug. 15, 1933. W. B. D. PENNIMAN I 2,

METHQD OF CRACKING HYDROCARBON OILS Original Filed March 6. 1922 Patented Aug. 15, 1933 1,922,322 METHOD" OF CRACKIgTG iirpaocaanon on.

William B. D. Penninian, Baltimore, Md.

Application March 6,

2 Claims.

This invention relates to a method of cracking hydrocarbon oils under pressure in which the heat required to maintain the cracking temperature is developed within the body of oil 5 under treatment, by combustion of the carbon formed by decomposition of the hydrocarbon.

In a prior application, Serial No. 526,707, filed Jan. 3, 1922, I have described a method in which .air is blown through liquid hydrocarbons, the temperature of the hydrocarbon being maintained sufliciently high for the oxygen of the air" to combine with the hydrocarbon to form various oxidation products.

In the former method, the air was preferably forced into the still with high velocity; and it was found in practice that the action of the oxygen is selective, a larger percentage of hydrogen than carbon being acted upon although in one particular oil used, the ratio of carbon to hydrogen was about 85% carbon to hydrogen. In a specific case analysis of the various products showed that 75.7% hydrogen'was converted into water while 252% carbon was burned to carbon dioxide.

Oxidized products of petroleum were also formed and recovered as has been fully described in the application above referred to.

As the lighter products of petroleum contain a higher percentage of hydrogen than the heavier products, it is desirable under certain market conditions to avoid the unnecessary formation of these oxidation products, and to burn or oxidize the less valuable carbon rather than the more valuable or more desirable hydrogen. This can be done by a modification of the apparatus described in my prior application, above referred to, the important difference being that in the modified apparatus the air instead-of being delivered into the body of the oil under high velocity is, through increase of the size of the nozzle, allowed to enter the oil with little or low velocity. The delivery end of the air pipe is placed at or near the bottom of a catch-basin so that carbon, for instance lamp black, formed by the process of cracking is retained by the basin and gradually slips down the side of the basin to the air jet.

At the temperatures prevailing in the still, as hereinafter described, the oxygen of the air combines with the carbon with generation of sufficient heat to maintain the body of oil at the desired cracking temperature. The heat thus generated is disseminated throughout the body of oil by the gaseous products of combustion which 11922, Serial No. 541,525

Renewed August 3, 1927 pass out of the still with the vapors and gases resulting from the cracking.

An apparatus for carrying out theprocess is shown in the accompanying drawing.

The apparatus consists of an upright still or drum having heavy walls adequate to sustain a pressure of 300 lbs. or more per sq. in. The still is preferably made in two sections A and B, secured together by companion flanges 3, 4 and suitable bolts. The still may be mounted above a gas-fired furnace of any suitable construction. Oil is introduced into the still by a pressure-pump 5, from which leads a delivery pipe 6, having, within the still head, a coil 7, and a depending delivery pipe 8. Air is forced into the still from a pump 9, through pipe 10, having a pressure gage ll, coil 12 (within the still), and depending pipe 13, provided at its lower end which is near the bottom of the still, with an upwardly. directed delivery nozzle It. This nozzle consists of a basinshaped receptacle into the bottom of which, the air-pipe opens. Blow-cocks l5, enable the level of the oil in the still to be ascertained. 16 is a blow-off line through which residual material is removed. l7, 17 are thermometer wells. 24 is a vapor line leading to condenser-coil 25, which is connected to collectingv tank 26, provided with a pressure-gage 27 and safety valve 28. The liquid collected in the tank 26, is delivered through pipe 29, and the uncondensed vapors and gases pass off through pipe 30, suitable storage or collecting vessels are, of course, connected to pipes 29 and 30.

The process is carried out as follows:

Oil is introduced into the still, either already at a temperature of about 400 F. or is raised to that temperature by the application of heat from the furnace below the still. Air under pressure is then blown into the still through the nozzle 14. The heat generated during the passage of the air upward through the deep body of oil, by oxidation of constituents of the hydrocarbon is suficient to raise the temperature to the desired cracking point, say 750 F. As the result of the cracking carbon is liberated, and this carbon which resembles lamp black in consistency, is deposited in the basin and mixed with a relatively small or no amount of oil, comes into contact with the entering air. The oxygen in the air combines with the carbon and causes combustion to take place with generation of suiiicient heat to maintain the temperature of the body of oil at the desired cracking point. The gaseous products of combustion ascending from the nozzle disseminate their heat throughout the body of oil which is thereby eifectively heated throughout its mass. The products of combustion escaping with the vapors are found to contain approximately 16% CO2 and 5% CO by volume, comparatively small amounts of water and oxidation products being formed. The cracking of the oil is thus carried on most largely by the heat generated by the combination of the oxygen of the air and the free carbon of the oil and hydrogen is consumed in relatively small amounts and in smaller ratio than the ratio of the hydrogen to the carbon as they exist in the oil used.

The preheating of the air and oil in the still head coils 7 and 12, not only saves heat, but these coils condense high-boiling fractions, which run back into the still. The order of the pressures used will be indicated by our practice, which as applied to Pennsylvania fuel oil, required a pressure from 300 to 325 lbs. The total pressure exerted on the surface of the coil is, therefore, due both to the partial pressure of the oil-vapors and to that of the deoxygenated air.

The quantity of air introduced is regulated so that practically the entire ozygen content thereof goes into chemical combination. Some air may pass through the oil unchanged, but its quantity is small and is not suificient to cause trouble. A constant volume of oil is maintained in the still and the air and oil are continuously delivered to the still at such rate that the temperature and pressure therein are maintained at the desired points for the production of the desired product.

The pressure employed is" not an arbitrary constant but is determined by the material being treated. Thus a higher pressure is necessary in treating oils like kerosene than heavier oils, such as fuel oils. My work indicates the limits of preferable pressures as between 50 and 500 lbs., though lower. pressures may possibly be used, and it may be advantageous to use higher pressures. So also my invention is not limited to any specific temperatures, as these will vary with the material operated upon. The temperatures to which the liquid oil must be raised for efiective crackingare either within the knowledge of those skilled in the art or can be readily determined by experiment. Broadly stated the limits may be given as 500- 1000 F. and generally higher than 700 F.

It is at times desirable to use steam in conjunction with the air. This steam can be introduced at any convenient point in the still, but I prefer to introduce it, as by pipe 51, mingled with the air,

through the air pipe and nozzle. The mixture of air and steam when brought in contact with the carbon that has been caught in the basin, reduces the temperature at the combining point and a portion of the steam is decomposed with the formation of carbon monoxide and hydrogen. The amount of steam used is relatively small, generally from 5%50% (by volume) of the air used.

I claim:

1. A process of cracking heavy hydrocarbon oil 30 under pressure and a maintained cracking temperature, which consists in injecting air into the body of oil, collecting carbon resulting from the cracking adjacent to the point of air injection, and maintaining the cracking temperature of the 35 oil by the heat resulting from combustion of the carbon and air. I

2. A process of cracking heavy hydrocarbon oil under pressure and a maintained cracking temperature, which consists in injecting air and steam into the body of oil, collecting carbon resulting from the cracking adjacent to the point of air injection, and maintaining the cracking temperature of the oil by the heat resulting from combustion of the carbon and air.

3. In a process of cracking a body of heavy hydrocarbon oil to produce lighter hydrocarbons, the method of supplying the heat needed, which consists in collecting carbon as it is produced active contact therewith, whereby combustion ensues. I

a. The method as claimed in claim 3 in which steam is mingled with the air.

5. In a process of treating heavy hydrocarbon oil to produce lighter hydrocarbons, the step of passing air into a body of such oil at a velocity reduced sufiiciently to allow carbon formed during the process to collect at the point of air entry.

6. A process of treating heavy hydrocarbon oil to produce lighter hydrocarbons which comprises passing air into a body of such oil of deoxygenating depth under pressure and at a cracking temperature, collecting carbon as it is formed within the body of oil, and bringing air into reactive contact therewith whereby combustion ensues.

7. The process of treating hydrocarbon oil which comprises subjecting the oil to the action of heat and pressure in the presence of oxygen to form products including lighter hydrocarbons and carbon, and burning in the treatment zone at least a part of the carbon thus formed to supply at least a part of the heat required in the first-named conversion step.

8. The process of treating hydrocarbon oil which comprises subjecting the oil to the action of heat under pressure in the presence of oxygen and steam to form products including lighter hydrocarbons and carbon, and burning in the treatment zone at least a part of the carbon thus formed to supply at least a part of the heat re-. quired in the initial conversion step.

WILLIAM B. D. PENNIMAN. 

